Why did Anne Frank begin to write a diary?

Anne Frank was trapped in very small spaces with her sister, parents, another family, and another man for around two years. She was thirteen years old, which means she was entering adolescence. This is a time when most children would experiment with makeup and talk with their girlfriends about crushes. Anne was instead stuck in a tiny space with no privacy. She sought relief in what she had, and what she had was a little autograph book she had gotten for her birthday. Here, writing in the form of letters to an unknown friend, she could admit her secret thoughts, fears, hopes, and dreams. This was the only privacy, the only thing that belonged solely to her, that Anne had in her life for two years, as she grew from a little girl to a young woman.